fix(v2): ignore hash changes in useChangeRoute hook (#5023)

* fix(v2): ignore hash changes in useChangeRoute hook

* refactor and introduce useLocationChange hook

Co-authored-by: slorber <lorber.sebastien@gmail.com>

packages/docusaurus-theme-common/src/utils/usePrevious.ts

@@ -0,0 +1,18 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {useRef, useEffect} from 'react';
+
+export function usePrevious<T>(value: T): T | undefined {
+  const ref = useRef<T>();
+
+  useEffect(() => {
+    ref.current = value;
+  });
+
+  return ref.current;
+}